In this work, we fabricated the graphite nanoplatelets (GNPs)-based thermal conductive materials (TCMs) via the gap-coating method. Remarkably, the TCMs have a prominent heat conduction coefficient of 36.44 W/mK, which is attributed to the aligned graphite nanoplatelets. Viscosity is a key factor for the alignment of the fabricated composite. Polarized Raman spectroscopy was performed on the transverse sections of the composite to detect the orientation degree, and the intensity of the 2D Raman peak is sensitive to these anisotropic properties. Furthermore, Polarized Raman spectroscopy is initially employed for calculating interfacial thermal resistance (ITR) in samples with different viscosities. The orientation factors were 0.35 and 0.23, while the ITR values were 5.20 x 10-6 m2 K W- 1 and 5.91 x 10-6 m2 K W- 1 respectively. These values correspond to an increase in viscosity from 223 mPa center dot s to 559 mPa center dot s, confirming the effect of viscosity on both orientation degree and interfacial thermal resistance. This approach also provides a promising new method for detailed ITR determination in well-dispersed thermal conductive materials.

Wearable heaters are essential for people living in cold regions, but creating heaters that are low-cost, lightweight, and high air permeability poses challenges. In this study, we developed a wearable heater using carbon nanotube/water polyurethane (CNT/WPU) nanocomposite fibers that achieve high extension rate and conductivity. We produced low-cost and mass-produced fibers using the wet spinning. With heat treatment, we increased the elongation rate of the fibers to 1893.8% and decreased the resistivity to 0.07 omega*m. then wove the fibers into a heating fabric using warp knitting, that resistance is 493 omega. Achieved a uniform temperature of 58 degrees C at voltage of 36 V, with a thermal stability fluctuation of -5.0 degrees C to +6.3 degrees C when bent from 0 degrees to 360 degrees. Our results show that wearable heaters have excellent flexibility and stretchability, due to nanocomposite fibers and special braided structure, which offer a novel idea for wearable heaters.

Stretchable conductors (SCs) have shown promising potential in the field of stretchable electronic devices for their lightweight, high flexibility, stable performance, and easy integration. However, the conductivity of most reported stretchable conductive composites is sensitive to deformation, and it is still unsatisfactory due to their poor recoverability and low reliability under large strain. In this paper, we have fabricated a serpentine stretchable conductor (SSC) with high conductivity, stretchability, and ultra-stability by spontaneously wrapping elastic waterborne polyurethane (WPU) sheath on the surface of the multi-walled carbon nanotube (MWCNT)/ WPU nanocomposite conductive yarn, which was prepared by a simple wet-spinning method. The WPU elastic sheath endows SSC with long-term tensile durability and recoverability. Remarkably, benefiting from the sharing effect of the serpentine structure on the tensile strain energy, SSC shows distinctive strain-insensitive behavior (Delta R/R0 less than 1.6%) up to 100% strain and ultra-high quality factor (Q = 105) at 80% strain. Furthermore, SSC also has temperature resistance, waterproof ability, and self-healing capability, making it capable of being used in harsh circumstances. The combination of high conductivity, stretchability, and super reliability renders many potential applications for SSC, such as stretchable interconnects and wearable heaters. Such serpentine stretchable device with distinctive strain-insensitive behavior provides a novel design idea for stretchy electronics.

In recent years, artificial muscle is of great research interest due to its promising application. However, low deformation, complicated fabrication process, and high cost hinder their development. Herein, electro-thermally driven biaxial bending artificial muscle based on oriented graphite nanoplate nanocomposite (GN)/polyimide (PI) complex structure is successfully fabricated by cost-effective process utilizing coefficient of thermal expansion difference between them. GN/PI bi-layer films were further assembled and packaged into multi-unit biaxial bending actuator, which could extend and contract like artificial muscle. The unique characteristics of large deformation, easy control, low cost and simple fabrication process distinguish the GN/PI bi-layer based artificial muscle from others. Driven by the voltage of 10 V, the artificial muscle could reversibly reach a shrinkage rate of 11% and a maximum lifting height of 2.5 cm with the object weight of 5.0 g. Moreover, a walking robot has also been designed to achieve a large displacement.

Electrothermal materials have been widely used due to controllable heat energy in our life. With the development of wearable technology, a flexible, safe and waterproof heater with the good ability to endure repeated bending is required in future. In this paper, we have developed a novel wearable heater based on flexible, stretchable graphite nanoplates and polyurethane (GNP/PU) nanocomposite films. Firstly, the GNP/PU thin films with a thickness of 30-200 mu m were fabricated in mass production by the method of gap-coating, which can be bent 180 degrees repeatedly, or even knotted for their excellent flexibility, and has a maximum elongation up to 387.8%, due to the homogenous distribution of GNP in PU matrix. By the control on the amount of GNP and the thickness of the film, the minimum resistivity and square resistance of the GNP/PU films can be 80 m Omega.cm and 4 Omega/square, respectively. Through a further flexible structure designing and waterproof electronic packaging process, the fabricated wearable heaters are able to withstand 100,000 180-degrees bending with the resistance changes of only 3.24%, and have a IPX7 waterproof ability to work continuously for 120 min under 1.30 m water. Interestingly, as-prepared bare GNP/PU films have a good resistence to water and salt erosion, with the light 2.1%, 2.4% and 3.1% increasing in electrical resistance, and without obvious change in heating performance, even after the immersion in pure water, 0.5% and 5% salt water and dried completely. Furthermore, the wearable heaters can generate heat uniformly under the safe voltage of 5-24 V to achieve rapid heating and cooling rate of 25 degrees C/min and 13 degrees C/min, respectively. Lastly, a heating full-body vest mode of as-prepared wearable heaters was fabricated, which can work well with hand raising, bending and walking. The results showed that as-prepared wearable heaters were very suitable for wearable electronics, due to the excellent flexibility and stretchability of GNP/PU films and their special packaging structure, which provides a new choice for wearable heating products.

High efficiency and broad bandwidth wave absorption materials are urgent need in daily life for human health. Carbon material (graphene, etc.) is widely used in electromagnetic wave (EMW) absorption field for light weight, high surface area, and excellent electrical conductivity. However, the immoderate conductivity of the carbon will also cause the impedance mismatch and need more consideration. We have synthesized sucrose-derived carbon-based hybrid absorbers, and a series of Ni-based alloys (Ni, Fe–Ni, Co–Ni) are decorated on the surface of the carbon. Consequently, the Ni/C composite shows a maximum attenuation constant, and an ultra-broad wide effective bandwidth of 6.24 GHz with an optimal reflection loss (RL) value of − 20.5 dB located at thickness of only 1.7 mm. The Co–Ni/C composite has an improved impedance matching level, and shows the optimal RL of − 34.3 dB located at a thickness of 3.3 mm with an effective bandwidth of 4.24 GHz. The Fe–Ni/C composite shows an optimal RL among all the samples of − 42.3 dB located at a thickness of 5.7 mm with the effective bandwidth of 2.8 GHz. The Ni-based alloys decorated sucrose-derived carbon hybrid can be a proper candidate for microwave absorption as its light-weight outstanding EMW absorption property. The Ni-based alloys decorated sucrose-derived carbon hybrid for microwave absorption

Since the "net-zero " goal was proposed, wind power has been developed rapidly in recent years. Due to its largescale installations in cold regions, the icing of wind turbine blades is currently one of the main limitations for efficient operation. In response to this issue, a highly reliable, flexible, stretchable, and lightweight in-situ deicing heating system based on the CNT/WPU nanocomposite films was developed. The CNT/WPU thin films were fabricated by the roll-to-roll gap-coating and hot-pressing process leading to as-prepared CNT/WPU film heaters have so outstanding reliability that they can withstand 100,000 times 240 bending with the resistance fluctuation of 3.17 %, and the repeated stretching of 2.0 % strain in the length direction without any impact on their temperature distribution, and even the weak impact with 10 % strain. The films may have promising potential applications in various curved surface heating with strict requirements on reliability in the future.

Thermal interface materials (TIMs) play a crucial role in enhancing the reliability and sustainable utili-zation of next-generation electronics and thus can help meet the increasing demand for multifunctional devices with higher performance. Herein, we introduce a method for creating a TIM with high cross-plane thermal conductivity based on graphite nanoplatelet (GNP)/polyurethane (PU) films. The graphite nanoplatelets ensured the heat transfer properties of the TIM. Moreover, the hot-pressing procedure improved the thermal conductivity to 26.3 W (m K)(-1) with the improved orientation of the GNPs in the PU matrix, as confirmed by microscopy investigation. Under a thermal dissipation power of 10-20 W, a drastic reduction in the chip temperature (17.5-42.3 degrees C) was achieved using our oriented GNP/PU TIM compared to a commercial silicone TIM (5.0 W (m K)(-1)). In addition, as-prepared pads can be mass produced at an acceptable cost, indicating that our work provides a promising new approach to fabricating TIMs for application in the next-generation thermal management of high power density electronics. (C) 2021 Elsevier Ltd. All rights reserved.

As the huge demand for a multifunctional electronic device with high performance, an important technology in next-generation electronics is thermal management and there are numerous uses for it in enhancing the reliability and sustainable utilization. In this work, a high thermal conductivity substrate based on graphite nanoplatelets (GNPs)/ polyurethane (PU) nanocomposite film is fabricated. The GNPs' orientation can be semiquantitative controlled by balancing the effect of gravity and micro-flow field, which results in a thermal conductivity varies from 38.1 W (m.K)-1 to 19.8 W (m.K)-1 as the orientation rearrangement. Meanwhile, Interfacial thermal resistance is evaluated by the Effective medium theory (EMT) models, which is about 1.76 x 10-6 K m2/ W to 2.0 x 10-6 K m2/W at 30 degrees C. Additionally, the chip fixed to the GNP/PU substrate (38.1 W (m.K)-1) could work under a lower temperature than the commercial polycarbonate substrate. Our method is a promising strategy for thermal management of next-generation electronics devices.

In future, thermal management will play a crucial role in their design and fabrication, because the rapid development in miniaturization and versatility of electronic devices leads to the huge increase in power density. It is an inevitable trend to develop flexible substrate materials with high thermal conductivity, high heat flux, excellent stability and reliability. In this work, a new flexible print circuit board (G-FPC) containing a graphene film with sandwich structure was fabricated for heat dissipation. Firstly, multi-layer graphene film (M-GF) with 739.56 W m−1 K−1 in-plane thermal conductivity was prepared by high-temperature heat treatment (2900 °C) of GO film followed compression rolling process. Then, as-prepared M-GF and polyimide (PI) film were laminated and hot-pressed to fabricate G-FPC with epoxy resin as adhesive. As-fabricated G-FPC exhibits excellent flexibility, stability, and reliability, whose in-plane thermal conductivity can remain 98%, 81% and 88% after 10000, 15,000 and 20,000 bending times. Moreover, as-fabricated G-FPC has good heat dissipation capacity, which can significantly reduce chip temperature, 10 °C lower than traditional FPC with the power density of 0.42 W/cm2. The G-FPC with sandwich structure of PI/M-GF/PI will have potential applications in the flexible and wearable electronics in future, due to their versatility in heat dissipation, flexibility, stability and electronic interconnection as substrates.

Flexible strain sensors, as crucial components in smart wearable devices, have recently drawn considerable attention due to their long-term monitoring abilities and facile interaction with the human body. However, low sensitivity, sluggish response, poor repeatability, sophisticated, and expensive fabrication process have notoriously limited their further deep applications. Herein, a graphite nanoplatelet (GNP) based capacitive-type strain sensor has been developed by a cost-effective gap coating method. The prepared sensors can be stretched up to 30%, and unlike other traditional capacitive-type strain sensors which have a limited theoretical maximum gauge factor of 1, it exhibits an interesting negative gauge factor, whose absolute value can go up to ∼3.5. Additionally, this work also investigated the layout design of shunt capacitors, and the pseudo-interdigital capacitor sensor demonstrated a substantial increase in the cyclic stability compared to the parallel plate capacitor. Furthermore, the as-prepared sensor has a fast signal response, whose response time is less than ∼140 ms and recovery time less than ∼90 ms. Also, the cyclic stability test of stretching proves the long-term durability of the sensor. Moreover, a microcontroller unit (MCU) system has been developed in the circuit level to realize the real-time control of a robotic hand.

通过对Cu/Sn-58Bi/Cu互连接头在120℃时效0天、1天、3天和5天试验,观察界面化合物在接头表面生长与演化;发现Sn-58Bi/Cu界面化合物表面具有2种形貌:靠近钎料端的界面化合物大而紧实;靠近铜端小而松散,呈颗粒状;化合物生长速率在时效初期(0～3天)非常迅速,认为是Cu6Sn5控制的化合物生长过程;3～5天的化合物生长,主要由消耗Cu6Sn5形成Cu3Sn的过程控制,化合物生长变慢.

The effect of In on melting property, microstructure and mechanical properties of Sn–40Bi–xIn (x = 0, 1, 2, 4, 6, 8 wt%, respectively) alloys was investigated by means of differential scanning calorimetry, scanning electron microscope, X-ray diffraction and tensile test. The results show that the solidus temperature and the liquidus temperature decrease with the increase in In content. The 1In, 2In and 4In alloys are composed of Sn–Bi eutectic and β–Sn dendrites with In atoms dissolved, whereas 6In and 8In alloys composed of Sn–Bi eutectics, BiIn–Sn metastable phases, Bi particles and primary β–Sn phases. At room temperature, 6In exhibits the maximum ultimate tensile strength of 77 MPa, while 4In displays a more outstanding elongation rate of 42%. Moreover, 2In alloy exhibits an even outstanding elongation behavior (above 300%) at temperatures of 100 and 120 °C.

The effects of Cu additions (varied from 0.1, 0.3, 0.5, 0.7 to 1 wt% respectively) on melting properties, microstructures and mechanical behaviors of Sn–40Bi alloys have been investigated. The experimental results show that Cu addition does not make an obvious difference to the onset of melting range. Instead, it narrows the glass transform range down by 7.8 °C. Further, it refines the microstructure and improves the ultimate tensile strength of solder alloys with increasing Cu addition at room temperature, while the elongation increases remarkably first and then decreases after adding 3 wt% Cu at high temperature, 5 wt% at room temperature respectively. The microstructures for Sn–40Bi–xCu alloy are arranged by Sn-rich dendrites with Bi precipitates in their own core surrounded by a complex eutectic mixture (Bi-rich and Sn-rich phases) and intermetallic compound, Cu6Sn5 and Cu3Sn. The optimum alloy based on mechanical properties in this work is Sn–40Bi–0.3Cu, which shows an 131 percent elongation, a rupture fracture at 120 °C.

Effects of reflow time on the interfacial microstructure and shear strength of the SAC/FeNi-Cu connections were investigated. It was found that the amount of Cu6Sn5 within the solder did not have a noticeable increase after a long time period of reflowing, indicating that the electro-deposited FeNi layer blocked the Cu atoms effectively into the solder area during a long period under liquid-conditions. The ball shear test results showed that the SAC/FeNi-Cu joint had a comparable strength to the SAC/Cu joint after reflowing, and the strength drop after reflowing for 210 s was less than that of the SAC/Cu joint.